Abstract: Sandstone is the most common rock type for geological relic and historic stone. Lithologic deterioration induced by freeze-thaw is the dominant reason that cause sandstone geological disaster. Permeability reduction and physico-mechanical property improvement is an effective way to solve this problem. In this study, the feasibility using Microbial Induced Calcite Precipitation (MICP) to improve the freeze-thaw resistance of sandstone with various types of porosity was studied as well as its mechanism was analyzed. MICP treatment and freeze-thaw test were carried out based on two types of sandstone with mediumgrain size and fine-grain size. Experimental results indicate that (1) MICP treatment could improve the freeze-thaw resistance of the two types of sandstone, which is contribute to the production of the CaCO3 crystals during the MICP process. These CaCO₃ crystals occupy the porosity and reduce the volume of pore water and damaging force as well as enhance the bonding of the stone particles. However, MICP improvement performance is affected the effect of porosity. (2) After 40 cycles of freeze-thaw test, apparent damages at angular position were only observed from the samples without MICP treatment compared to the samples with MICP treatment. (3) The reduction rate of porosity of sandstone with medium-grain size and fine-grain size were reduced to 4.4% and 6.3% from 17.0% and 14.8% due to the MICP improvement when subjected to 40 cycles of freeze-thaw test. The same phenomenon can also be observed from the mass loss rate, water absorption, the reduction rate of wave velocity, corresponding values are 0.04% and 0.02% from 0.22% and 0.14%, 0.75% and 1.5% from 6.8% and 4.4%, 7.3% and 3.8% from 18.5% and 12.4%. (4) The efficiency of MICP process, effective treatment depth, distance of pore near surface of sandstone with mediumgrain size were higher because that its pores are larger, inducing higher values of the reduction rate of porosity and water absorption, growth rate of mass and wave velocity.

Key words: microbial induced calcite precipitation, MICP, sandstone, porosity, Freeze-Thaw